System preventing double digit detection caused by in-band dual-tone multi-frequency signaling and methods thereof

ABSTRACT

A T2P (TDM to packet) delay buffer is provided. The delay buffer can prevent double digit detections caused by in-band DTMF leak when out-of-band DTMF is used. The T2P delay buffer is initialized with an audio pattern that represents silence in a configurable amount of delay. When a DTMF digit is detected, the system can stop taking the voice payload from the T2P delay buffer and start injecting RFC4733 RTP packets into the RTP stream at a pre-configured rate. The RFC4733 DTMF RTP packets continue to be injected into the RTP stream until the DTMF digit stops. Once the end of the DTMF digit is detected, the content of the T2P delay buffer can be discarded and the T2P delay buffer is reinitialized with an audio pattern that represents silence in a configurable amount of delay. After the T2P delay buffer is reinitialized, the voice packetization can be continued.

TECHNICAL FIELD

This disclosure generally relates to communications, and moreparticularly, to preventing double digit detection in a downstreamcircuit-switched network caused by in-band dual-tone multi-frequency(DTMF) leaks when the voice path goes through a packet-switched networkand out-of-band DTMF is used within the packet-switched network.

BACKGROUND

DTMF signaling is used in telecommunications as a form of signaling overanalog and digital telephone lines in the voice-frequency band betweentelephone handsets and other communication devices, as well as betweencommunication devices without human involvement. DTMF signaling and theprotocols based on the DTMF signaling were designed to work well incircuit-switched networks, where both the voice and the DTMF share thesame frequency band but cannot go through at the same time. Thus, theDTMF signaling in circuit-switched networks is said to be carriedin-band. The sending endpoint generates DTMF tones. The receivingendpoint, when required, listens for the DTMF tones by deploying adevice called a DTMF detector, a device that detects DTMF tones andreports them to call control.

To guard against false signal detection, for example voice detected as aDTMF tone, DTMF detectors have to be configured not to recognize DTMFsignals whose duration is below a certain minimum. To guard againsterroneous double digit detection, if a signal is interrupted by a shortbreak in transmission or by a noise pulse and once the DTMF digitdetection has started, interruptions shorter than a specified minimummust not be recognized by DTMF detectors. As an example of double digitdetection, when a sending endpoint sends DTMF signals “123456789”, theDIME detector at the receiving endpoint could detect and report“11234556678899”.

If the DTMF has to go through a packet-switched network, it can becarried either in-band or out-of-band. When DTMF signaling is carriedin-band through a packet-switched network, the DTMF is treated as voiceand the DTMF signaling goes through the packet network undetected. Thereare several issues with carrying DTMF signaling in-band throughpacket-switched networks. First, only some voice codecs, for exampleG711, can encode the DTMF signal accurately. Most compression algorithmswould change the signal in such a way that it cannot be detectedreliably after decoding. This means that packet-switched networks wouldnot be able to take advantage of voice compression when DTMF signalingis required in a call. Second, packet jitter, packet delay, and/orpacket loss, all of which are inherently present in packet-switchednetworks, can cause breaks in DTMF signals that are longer than theaccepted minimum. As a result, DTMF detectors could interpret such DTMFsignals either as double digits or digits can go undetected alltogether.

To avoid those issues described above, a more reliable method forcarrying DTMF through packet-switched networks is devised whereby DTMFsignals are detected via DTMF detectors at the ingress of thepacket-switched network and then sent as special DTMF signaling packetsinto the packet-switched network, either as a substitute for the in-bandDTMF, or concurrently with the packetized in-band DTMF, and thus thename out-of-band DTMF. One example of a packet-switched network is an IPnetwork and an example of a protocol used to transport voice through anIP network is RTP, specified in IETF documents RFC3550/RFC3551, andRFC4733, that describes how to carry DTMF signaling, other tone signalsand telephony events in RTP packets, that is, out-of-band.

The process of detection of DTMF signals takes a finite amount of time.Once a DTMF signal is detected, the DTMF detector reports this event tocall control. It takes a certain amount of time for this to be processedby call control and for out-of-band DTMF signaling packets to begin tobe injected. During this time the in-band DTMF continues to be carriedthrough and represents in-band DIME leak.

If a call carrying out-of-band DTMF signaling is terminated within thepacket-switching network, the receiving endpoint within this networkconsumes the special DIME signaling packets, for example RFC4733 RTPpackets, and the DTMF signaling stays in out-of-band form. The leakedthrough in-band DTMF does not impact the ability of the receivingendpoint to recognize and interpret the out-of-band DTMF signalingpackets and to act upon them. Even though the leaked in-band DTMF couldbe heard at the receiving endpoint, this does not impact the signalingdecisions of the receiving endpoint because the receiving endpoint actsupon the out-of-band DTMF signals rather than upon the in-band DTMFsignals.

If, on the other hand, the packet-switching network is just anintermediate network and the call has to be routed back into acircuit-switched network to reach its receiving endpoint, theout-of-band DTMF signaling has to be converted back to in-band DTMF format the egress of the packet-switching network before it can be insertedinto the circuit-switched network. Now a mix of the leaked in-band DTMFand the regenerated in-band DIME is used. Depending on the amount of theleaked in-band DTMF, its relative position and phase to the regeneratedin-band DTMF, and characteristics of the downstream DIME detector,either the one at the receiving far endpoint or another intermediate onethe DTMF detector can interpret this as a double digit.

A need therefore exists for a system preventing double digit detectioncaused by in-band DTMF signaling and methods thereof that overcome thoseissues described above. These, as well as other related advantages, willbe described in the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

The novel features believed to be characteristic of the disclosure areset forth in the appended claims. In the descriptions that follow, likeparts are marked throughout the specification and drawings with the samenumerals, respectively. The drawing FIGURES are not necessarily drawn toscale and certain FIGURES can be shown in exaggerated or generalizedform in the interest of clarity and conciseness. The disclosure itself,however, as well as a preferred mode of use, further objectives andadvantages thereof, will be best understood by reference to thefollowing detailed description of illustrative embodiments when read inconjunction with the accompanying drawings, wherein:

FIG. 1 is a block diagram illustrating in-band DTMF leaks causing doubledigit detections in a downstream circuit-switched network caused byin-band DTMF leaks when the voice path goes through a packet network andout-of-band DTMF is used within the packet network in accordance withone or more aspects of the present disclosure;

FIG. 2 is a block diagram depicting typical components of a TDM to IPand/or IP to TDM voice call in accordance with one or more aspects ofthe present disclosure;

FIG. 3 is a flow chart showing illustrative procedures for initializinga T2P delay buffer in accordance with one or more aspects of the presentdisclosure;

FIG. 4 is a flow chart showing illustrative procedures for packetprocessing within a T2P data/voice path in accordance with one or moreaspects of the present disclosure; and

FIG. 5 is a block diagram depicting illustrative procedures forassembling packets for a T2P delay buffer in accordance with one or moreaspects of the present disclosure.

DESCRIPTION OF THE DISCLOSURE

The description set forth below in connection with the appended drawingsis intended as a description of presently preferred embodiments of thedisclosure and is not intended to represent the only forms in which thepresent disclosure can be constructed and/or utilized. The descriptionsets forth the functions and the sequence of steps for constructing andoperating the disclosure in connection with the illustrated embodiments.It is to be understood, however, that the same or equivalent functionsand sequences can be accomplished by different embodiments that are alsointended to be encompassed within the spirit and scope of thisdisclosure.

Generally described, the present disclosure relates to communications,and more particularly, to a system preventing double digit detectioncaused by in-band DTMF signaling and methods thereof. In an illustrativeembodiment, a T2P delay buffer is provided. The T2P delay buffer canprevent double digit detections caused by in-band DTMF leak whenout-of-band DTMF is used. During call setup, if the DTMF detection isrequired, the T2P delay buffer is initialized with an audio pattern thatrepresents silence in a configurable amount of delay that can bedependent on the amount of time it takes to detect the DTMF digit. Ifthe DTMF detection is not required, the T2P delay buffer is initializedwith zero delay. After the call setup, the voice path can beestablished. When a DTMF digit is detected in the voice path, the systemcan stop taking the voice payload from the T2P delay buffer and startinjecting RFC4733 RTP packets into the RTP stream at a pre-configuredrate, thereby leaving most of the audio payload that contains thebeginning of the detected in-band DTMF tone in the T2P delay buffer. TheRFC4733 DTMF RTP packets continue to be injected into the RTP streamuntil the in-band DTMF digit is detected to have stopped. Once the endof the DTMF digit is detected, the content of the T2P delay buffer canbe discarded and the T2P delay buffer is reinitialized with an audiopattern that represents silence in a configurable amount of delay thatcan be dependent on the amount of time it takes to detect the DTMFdigit. After the T2P delay buffer is reinitialized, the voicepacketization can be continued. Note that if the requirement to detectthe DTMF signals is no longer active, the T2P delay buffer can beinitialized with no delay added to it, thus reducing the round tripdelay when the DTMF detection is not needed.

A number of advantages can be offered by the illustrative embodimentdescribed above. The system can be less susceptible to jitter, delay andpacket loss than previous networks and systems. Because a cause ofdouble digit detection, in the context of the scenario described above,is addressed at the source of the DTMF signal leak, on the TDM to packetside (T2P) at the ingress of the packet-switched network, someconstraints on certain components on the packet to TDM side (P2T) can berelaxed. For example, and by way of a non-limiting illustration, theinitial play-out delay of the jitter buffer on the P2T side can bedecreased or even eliminated. Because the amount of delay added to theT2P delay buffer is configurable, if enough delay is added to the T2Pdelay buffer, the leaked in-band DTMF can be completely eliminated,which can be important in applications that require DTMF suppression,that is, elimination of the DTMF signals from the audio path. Manyadditional advantages of the present disclosure will become apparent tothose skilled in the relevant art as provided for in the followingdescription.

An exemplary environment for double digit detection caused by in-bandDTMF is provided in FIG. 1. FIG. 2 shows one embodiment of preventingdouble digit detection. FIGS. 3 and 4 depict flow charts forminimizing/eliminating in-band DTMF leak at the source of the leak, andthus preventing double digit detection in the context of the scenariodescribed above.

FIG. 5 shows processing of packets within the T2P delay buffer. TheseFIGURES are not intended to be limiting, but rather provided to disclosefeatures and concepts herein. Within the present disclosure, the T2Pdelay buffer can be referred to as an output queue. The T2P delay buffercan also be referred to as an egress packet queue. The T2P delay buffercan be implemented within hardware, software or combination of both.

FIG. 1 is a block diagram illustrating in-band DTMF leaks causing doubledigit detections in a downstream circuit-switched network caused byin-band DTMF leaks when the voice path goes through a packet network andout-of-band DTMF is used within the packet network in accordance withone or more aspects of the present disclosure. Double digit issues arisewhen the voice path goes through a packet network 106 and whenout-of-band DTMF signaling is used. As an example of double digitdetection, when a caller dials “123456789”, software can detect“11234556678899”.

To carry DTMF signaling over a packet network 106 reliably, the in-bandDTMF signaling coming from a Public Switched Telephone Network (PSTN)102 (circuit switched network) is converted into RFC4733 DTMF. Byconverting the in-band DTMF, the system 100 makes the DIEM signal lesssusceptible to jitter, delay and packet loss that is present in packetnetworks. Because the substitution of the in-band DTMF with RFC4733 DTMFtakes a finite amount of time to detect the in-band DTMF digit by thetime division multiplexer (TDM) to packet gateway 104, or voice gateway,a certain amount of the in-band DTMF leaks through at the source to thepacket network 106, that is, at the TOM to Internet protocol (IP)interface and gets carried together with the RFC DTMF through the packetnetwork 106.

The leaked in-band DTMF is then provided to the TDM to packet gateway108 (voice gateway) by the packet network 106. The in-band DTMF isregenerated from the RFC4733 DTMF at the egress of the packet-switchingnetwork 106, for example, the receiver propagates tone signalingaccurately into the PSTN 110 for machine consumption. In this scenario,it is possible that the leak gets interpreted as a double digit by a farend device if the amount of leaked in-band DTMF is sufficient.

Previously, if RFC4733 DIME in TDM-IP-TDM scenarios 100 were enforced,whether or not the leaked in-band DTMF made it back into the PSTN 110(circuit-switched network), depended on the amount of delay in thejitter buffer implemented by P2T in the TDM to packet gateway 108. Ifthe amount of accumulated audio in this jitter buffer was large enough,the leaked in-band DTMF would not be played out because the P2T wouldreceive the RFC4733 DTMF packet and start regenerating the in-band DTMFwhich would preempt playing the accumulated audio from the jitterbuffer. In P2T there are basically two queues, one for audio payload,the so called jitter buffer, and one for the DTMF digits. The P2Tprocesses RFC4733 DTMF at a higher priority compared to the audiopayload. So when there is enough audio payload accumulated in the P2Tjitter buffer and the in-band DTMF that leaked into the audio stream isat the tail end of the P2T jitter buffer, the received RFC4733 DTMFdigits could be played out before the accumulated audio that containsthe leaked in-band DTMF. Proper handling of the RFC4733 DTMF assumesthat the P2T audio jitter buffer gets emptied after the RFC4733 DTMFdigits are processed. So the amount of the accumulated delay in the TDMto packet gateway voice path P2T jitter buffer can be enough to mask theleaked in-band DTMF.

Nevertheless, in packet voice applications it is important to minimizedelay in the voice path. The lower the delay the less expensive the echocanceling. This translates to lower cost and greener products in termsof energy consumption. Therefore a goal is to decrease the P2T delay,and minimize or eliminate the amount of delay needed in the P2T jitterbuffer. In the past, there was no buffering on the T2P path, that is,there was no added delay in the T2P direction. Now, with the decreasedbuffering in the P2T direction, the P2T would underflow more frequently.In underflow conditions, the P2T can inject silence or perform a moresophisticated packet loss concealment algorithm. For the audio, thistypically does not cause any perceivable impact. If, however, the P2Tunderflow happens during the play out of the leaked in-band DTMF, thein-band DTMF can be interrupted. This in some cases can cause the doubledigit detection by the next in chain DTMF detector.

DTMF detection has been implemented on far end T2Ps in TDM-IP-TDMscenarios, for example a toll bypass application, to help generate DTMFon the near end more reliably so that network jitter would not result indouble digits if the DTMF would be carried in-band. Now that the RTPreceiver has to regenerate TDM DTMF from the RFC4733 DTMF, the excessiveamount of the leaked in-band DTMF, even when it ends up back-to-backwith the regenerated DTMF, can have a different phase compared to theregenerated DTMF and some DTMF detectors, that are sensitive to thephase, would treat this as two separate digits. Experiments have shownthat on an idle system, with a packet time set to ten (10) millisecondsand a DTMF detection report time of forty-eight (48) milliseconds, andno added delay in the T2P voice path, the in-band DTMF leak can be inthe amount of up to seventy (70) milliseconds.

In FIG. 1, the T2P 104 created an in-band DTMF leak. DTMF in its nativeform is in audio that can be received from a PSTN 102. RFC4733 DTMF, orthe like, was created to make the packet stream DTMF-aware. The in-bandDTMF signals from the PSTN 102 are replaced with out-of-band DTMFsignals that the packet network 106 knows how to process and deal with.DTMF digits can be detected within the incoming audio. A finite amountof time is required to detect the DTMF digit. Because of this lag,packetized data that should have been abandoned can be “leaked”. Afterthe in-band DIME leak goes through the packet network 106 and the TDM topacket gateway P2T 108, a far end device on the PSTN 110 can receivein-band DTMF having the leaked in-band DTMF and in-band DIME regeneratedout of the RFC4733 out-of-band DTMF. Because of the leaked in-band DTMF,it is possible that the device on the PSTN 110 can detect a doubledigit.

Turning now to FIG. 2, a block diagram depicting typical components of aTDM to IP (circuit-switched network 102 to packet-switched network 106)and/or IP to TDM (packet-switched network 106 to circuit-switchednetwork 102) voice call in accordance with one or more aspects of thepresent disclosure is shown. In-band DTMF S_(in) can be provided by thecircuit-switched network 102 to the T2P 214, which can represent acomponent of a TOM to packet voice gateway 104. S_(in) can include bothvoice and DTMF as they can share the same frequency band but generallynot at the same time.

From the circuit-switched network 102, S_(in) can be received by theecho canceller 208 where the voice quality within S_(in) can beimproved. The output S_(out) of the echo canceller 208 can in turn besent to a voice encoder 212. At the voice encoder 212, S_(out) can becompressed and converted for use by the T2P 214. To avoid unreliabledetection over the packet network, a DTMF detector 216 can be usedbefore S_(out) is sent to the packet-switched network 106 through theT2P 214. A delay buffer 502, shown in FIG. 5, can be placed within T2P214 providing additional delay for DTMF digit detection before packetsare sent out.

In operation, the DTMF detector 216 can determine whether a DTMF digitis within S_(out). A minimum amount of time is generally required beforea digit can be detected within the in-band DTMF resulting in S_(out)going through the voice encoder 212 and to the T2P 214, and storedwithin the delay buffer 502. By way of a non-limiting example, after atime of forty-eight (48) milliseconds, the DTMF detector 216 candefinitely say that a digit has been detected within S_(out). Theminimum duration below which a DTMF digit should typically not berecognized by the DTMF detector 216 can be between twenty (20)milliseconds to twenty-five (25) milliseconds. The minimum durationabove which a DTMF digit can be recognized is forty (40) millisecondsand the minimum signal interruption below which the digit should not berecognized as a new digit is between ten (10) milliseconds and twenty(20) milliseconds.

After detection of a DTMF digit, the DTMF detector 216 can provide aDTMF detection report to the call control 218 indicating that DTMF digithas been detected. The call control 218 can be alerted that there is adigit and processing of the digit should be handled. When a DTMF digitis detected, the system 200 can stop taking the voice payload from thedelay buffer 502 within the T2P 214 and start injecting RFC4733 RTPpackets into the RTP stream at a pre configured rate, thereby leavingmost of the audio payload that contains the beginning of the detectedin-band DTMF tone in the T2P delay buffer 502.

At the end of the DTMF digit, the DTMF detector 216 can also provide anadditional DTMF detection report to the call control 218. The RFC4733DTMF RTP packets can continue to be injected into the RTP stream untilthe DTMF digit stops. Once the end of the DTMF digit is detected, thecontent of the delay buffer 502 in the T2P 214 can be discarded and theT2P delay buffer 502 can be reinitialized with an audio pattern thatrepresents silence in a configurable amount of delay that can bedependent on the amount of time it takes to detect the DTMF digit. Afterthe T2P delay buffer 502 is reinitialized, the voice packetization ofthe audio can be continued. If the requirement to detect the DTMFsignals is no longer active, the T2P delay buffer 502 can be initializedwith no delay added to it. The call control 218 can determine the amountof audio that can be removed from the audio stream once a DTMF digit isdetected. A delay buffer 502 can provide a certain amount of delay intothe stream removing the possibilities of double digit detection. Thecontent of the delay buffer 502 can be discarded so the in-band DTMFdoes not get leaked to the receiving far end device.

The T2P delay buffer 502 along with the DTMF detector 216 and callcontrol 218 can remove the leaked in-band DTMF previously described,which led to the possibility of double digit detections. On the egressside coming from the packet-switched network 106, the in-band DTMF isregenerated from the RFC4733 DTMF at the P2T 204. The voice decoder 206can uncompress and convert the in-band DTMF R_(in) for use by the echocanceller 208. The echo canceller 208 can improve the voice qualitywithin R_(in), to R_(out) and provide R_(out) to the circuit switchednetwork 102.

FIG. 3 is a flow chart showing illustrative procedures for initializinga T2P delay buffer 502 in accordance with one or more aspects of thepresent disclosure. The delay buffer 502 can be used to provide aconfigured amount of delay to prevent double digit detection by a DTMFdetector 216 in the circuit-switched network 110. The delay buffer 502can prevent double digit detection caused by in-band DTMF leak when thevoice path goes' through a packet-switched network 106 and when usingRTP and RFC4733 by controlling the amount of leak at the source of theleak, that is, on the T2P 214. By limiting the amount of in-band DTMFthat leaks from the T2P 214, double digit detection can be prevented.The processes for initialization of the delay buffer 502 can begin atblock 300.

At decision block 302, the system 200 can determine whether DTMFdetection is required. The decision to detect DTMF can be based on anumber of factors such as whether other components can handle thein-band DTMF leak. If DTMF detection is not required, at block 304, thedelay buffer can be emptied, that is, a zero delay can be added to thebuffer 502. When, however, DIME detection is required, the call control218 can discard the contents of the delay buffer 502 and fill in thedelay buffer 502 with a silence pattern in a configured delay amount.The initialization processes can end at block 308.

FIG. 4 is a flow chart showing illustrative procedures for packetprocessing within a T2P data/voice path 104 in accordance with one ormore aspects of the present disclosure. The processes can illustratewhat happens in the data path as well as the voice path. Typically,these processes are repeated each tick time, for example, ten (10)milliseconds. The processes can begin at block 400. At decision block402, a determination can be made whether a DTMF digit has been detectedby the DTMF detector 218.

If a DTMF digit has not been detected, the T2P 214 can continue withvoice packetization of incoming TDM voice at block 408. When a DTMFdigit has been detected, at block 402, the T2P 214 can inject RFC4733DTMF into the stream until the DTMF digit has stopped, at block 404. Atblock 406, the T2P 214 can use the delay buffer initialization processesas described in FIG. 3. At block 408, voice packetization can becontinued. At block 410, the system 200 can wait for a period of time.This time can be configured based on the requirements of the system 200,for example, ten (10) milliseconds. Control can then be provided back todecision block 402. Through those processed described above, the delaybuffer 502 can be cleared of in-band DTMF leak and filled with a silencepattern to avoid double digit detection.

Referring to FIG. 5, a block diagram depicting illustrative proceduresfor assembling packets 510A, 5108, 510C, 510D, 510E and 510F(collectively packets 510) for a T2P delay buffer 502 in accordance withone or more aspects of the present disclosure is shown. As describedabove, the DTMF digit detection delay can require the use of a delaybuffer 502 that can be within the T2P 214. The T2P 214 can assemblepackets 510 in an assembly area 504 at the rate R_(i), represented as asingle box. R_(i) can be ten (10) milliseconds, that is, each packet 510can represent ten (10) milliseconds of TDM voice/data. Other rates canbe used, for example, five (5) or twenty (20) milliseconds, however, theminimum rate cannot be below the minimum supported outgoing packet ratein milliseconds.

An enquing rate R_(e) is a rate at which packets 510 are being providedto the delay buffer 502, while a dequeuing rate R_(d) is a rate at whichpackets 510 are being processed out of the delay buffer 502. P_(time)can represent the outgoing packet rate in milliseconds. In anon-limiting example, P_(time) can be from ten (10) milliseconds toeighty (80) milliseconds in steps of ten (10) milliseconds. BecauseP_(time) and R_(i) can differ, rate adaption is performed on the packet510 being assembled P_(a) 510E and 510F within the assembly area 504.When the packet P_(a) 510E and 510F reaches P_(time), it can get queuedfrom the assembly area 504 onto the delay buffer 502. The example inFIG. 5 demonstrates a case where P_(time) can be twenty (20)milliseconds and the configured DTMF detection report time can beforty-eight (48) milliseconds, and consequently the added T2P 214 delaycan be fifty (50) milliseconds.

The amount of the delay added to the delay buffer 502 can beconfigurable on a per call basis and can depend on whether DTMFdetection is required and the configured DTMF digit detection reporttime. For queue initialization, as shown above, if the DTMF detection isnot required, the amount of added delay can be zero (0) milliseconds.When the TDM to packet stream is opened, the silence pattern can bequeued onto the delay buffer 502 in the amount of the configured delay,P_(time) per packet. In one embodiment, the remaining amount of therequired delay gets added to a packet P_(a) 510E and/or 510F beingassembled.

When a DTMF digit gets detected, the system stops assembling packets 510in the assembly area 504 and stops both enqueuing packets 510 to thedelay buffer 502 and dequeuing packets 510 from the delay buffer 502,thus minimizing/preventing the in-band DTMF leak. The detected DTMFdigits start getting injected into the RTP packet stream in the form ofRFC4733 DTMF, for example, to the stream leading into the packetswitched network 106. When the end of the in-band DTMF digit getsdetected, injection of RFC4733 DTMF can stop. A silence pattern referredto as “sil” can get queued onto the delay buffer 502 in the amount ofthe configured of delay, P_(time) per packet. Any remaining amount ofthe required delay gets added to an assembled packet P_(a) 510E or 510Fin the assembly area 504. The system then restarts the process ofassembling packets 510 in the assembly area 502 and restarts bothenqueuing packets 510 to the delay buffer 502 and dequeuing packets 510from the delay buffer 502.

The minimum size of the delay buffer 502, in terms of number of packets510 that the delay buffer 502 has to accommodate, can depend on amaximum required delay to be inserted and R. Assuming that a practicalvalue for the inserted delay is a multiple of R_(i), then the minimumnumber of packets that the delay buffer 502 has to accommodate is amaximum amount of inserted delay divided by R. For example, if a maximumdelay is fifty (50) milliseconds and R_(i) is equal to ten (10)milliseconds, then the delay buffer 502 has to be able to accommodate atleast five packets 510. As shown in FIG. 5, the packets 510 can fill thedelay buffer 502 as well as a portion of the assembly area 504.

When a DTMF digit is detected, the injected amount of delay into thedelay buffer 502 can be determined such that the amount of in-band DTMFleak should not cause double DTMF digits. It is recommended to processpacket enquing into the delay buffer 502 prior to packet dequeuing fromthe delay buffer 502 to avoid additional processing delay. Recommendedvalues for the delay can depend on the configured DTMF detection reporttimes and R. If for example, R_(i) is ten (10) milliseconds, therecommended values can be:

Configured DTMF Detection Report Time Inserted Delay 32 ms 30 ms 48 ms50 ms 64 ms 70 ms

The data structures and code, in which the present disclosure can beimplemented, can typically be stored on a non-transitorycomputer-readable storage medium. The storage can be any device ormedium that can store code and/or data for use by a computer system. Thenon-transitory computer-readable storage medium includes, but is notlimited to, volatile memory, non-volatile memory, magnetic and opticalstorage devices such as disk drives, magnetic tape, CDs (compact discs),DVDs (digital versatile discs or digital video discs), or other mediacapable of storing code and/or data now known or later developed.

The methods and processes described in the disclosure can be embodied ascode and/or data, which can be stored in a non-transitorycomputer-readable storage medium as described above. When a computersystem reads and executes the code and/or data stored on thenon-transitory computer-readable storage medium, the computer systemperforms the methods and processes embodied as data structures and codeand stored within the non-transitory computer-readable storage medium.Furthermore, the methods and processes described can be included inhardware modules. For example, the hardware modules can include, but arenot limited to, application-specific integrated circuit (ASIC) chips,field-programmable gate arrays (FPGAs), and other programmable-logicdevices now known or later developed. When the hardware modules areactivated, the hardware modules perform the methods and processesincluded within the hardware modules.

The technology described herein can be implemented as logical operationsand/or modules. The logical operations can be implemented as a sequenceof processor-implemented executed steps and as interconnected machine orcircuit modules. Likewise, the descriptions of various component modulescan be provided in terms of operations executed or effected by themodules. The resulting implementation is a matter of choice, dependenton the performance requirements of the underlying system implementingthe described technology. Accordingly, the logical operations making upthe embodiment of the technology described herein are referred tovariously as operations, steps, objects, or modules. It should beunderstood that logical operations can be performed in any order, unlessexplicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language.

Various embodiments of the present disclosure can be programmed using anobject-oriented programming language, such as SmallTalk, Java, C++, Adaor C#. Other object-oriented programming languages can also be used.Alternatively, functional, scripting, and/or logical programminglanguages can be used. Various aspects of this disclosure can beimplemented in a non-programmed environment, for example, documentscreated in HTML, XML, or other format that, when viewed in a window of abrowser program, render aspects of a GUI or perform other functions.Various aspects of the disclosure can be implemented as programmed ornon-programmed elements, or any combination thereof.

The foregoing description is provided to enable any person skilled inthe relevant art to practice the various embodiments described herein.Various modifications to these embodiments will be readily apparent tothose skilled in the relevant art, and generic principles defined hereincan be applied to other embodiments. Thus, the claims are not intendedto be limited to the embodiments shown and described herein, but are tobe accorded the full scope consistent with the language of the claims,wherein reference to an element in the singular is not intended to mean“one and only one” unless specifically stated, but rather “one or more.”All structural and functional equivalents to the elements of the variousembodiments described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the relevant art areexpressly incorporated herein by reference and intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims.

What is claimed is:
 1. A method for preventing double digit detection ina downstream circuit-switched network caused by in-band dual-tonemulti-frequency (DTMF) leaks when a voice path goes through apacket-switched network and out-of-band-DTMF is used within thepacket-switched network, the method comprising: receiving audio;packetizing the audio into a delay buffer in a time division multiplexerto packet network direction; discontinuing packetization of the audiowhen a DTMF digit is detected; injecting DTMF signaling packets for theDTMF digit until the DTMF digit stops; discarding contents within thedelay buffer; filling the delay buffer with a silence pattern; andrestarting packetization of the audio.
 2. The method of claim 1,comprising initializing the delay buffer.
 3. The method of claim 1,comprising acquiring the audio from a circuit-switched network.
 4. Themethod of claim 1, comprising continuing with packetizing the audio whenthe DTMF digit is absent otherwise discontinuing packetization.
 5. Themethod of claim 1, wherein discarding contents within the delay buffercomprises removing an in-band DTMF leak within the delay buffer.
 6. Themethod of claim 1, wherein filling the delay buffer with the silencepattern comprises adding a configurable amount of delay.
 7. The methodof claim 6, comprising filling a remaining amount of the configurableamount of delay into at least one additional packet outside of the delaybuffer.
 8. The method of claim 6, comprising determining a time todetect the DTMF digit to add the configurable amount of delay.
 9. Adevice comprising: at least one processor; and a memory operativelycoupled to the processor, the memory storing program instructions thatwhen executed by the processor, causes the processor to: receive audio;packetize the audio into a T2P delay buffer; discontinue packetizationof the audio when a DTMF digit is detected; inject DTMF signalingpackets for the DTMF digit into a packet network until the DTMF digitstops; discard content of the T2P delay buffer; place a delay into theT2P delay buffer by filling it with silence pattern; restartpacketization of the audio.
 10. The device of claim 9, wherein the delayplaced into the T2P delay buffer is configurable and dependent ondetection of the DTMF digit.
 11. The device of claim 9, wherein thedelay is zero (0) milliseconds when the DTMF digit detection requirementis absent.
 12. The device of claim 9, wherein the delay is dependent ona time to detect the DTMF digit.
 13. The device of claim 9, whereinadditional delay is placed into at least one packet outside of said theT2P delay buffer.
 14. The device of claim 9, wherein the T2P delaybuffer holds a minimum number of packets to accommodate a maximum amountof the delay.
 15. A system comprising: a time division multiplexer topacket side delay buffer for preventing double digit detection caused byin-band DTMF leak when out-of-band DTMF is used, wherein packetizationof audio is stopped when a DTMF digit is detected, DTMF signalingpackets injected into a stream for the DTMF digit, packets within thedelay buffer discarded and a configured amount of silence added to thedelay buffer.
 16. The system of claim 15, wherein the DTMF signalingpackets are injected into the stream until the DTMF digit stops.
 17. Thesystem of claim 15, wherein the configured amount of silence isdependent on a detection time of the DTMF digit.
 18. The system of claim15, wherein the DTMF digit is detected when the audio represents theDTMF digit for more than forty (40) milliseconds.
 19. The system ofclaim 15, wherein a new DTMF digit is detected when the audio isinterrupted between ten (10) milliseconds to twenty (20) milliseconds.20. The system of claim 15, wherein the packets injected into the streamfor the DTMF digit are RFC4733 DTMF.